One of the goals of reconstructive surgery is to be able to replace damaged tissue with new tissue, perhaps grown from a patient's own cells. For example, researchers have endeavored to develop cartilage regeneration systems in which isolated chondrocytes are injected into a damaged area in the context of a polymer scaffold (see, for example, Atala et al., J. Urol. 150:747, 1993; Freed et al., J. Cell. Biochem. 51:257, 1993 and references cited therein). Similar seeded scaffold systems have been studied in the context of bone repair, where osteoblast cells are utilized in conjunction with polymeric or ceramic supports (see, for example, Elgendy et al., Biomater. 14:263, 1993; Ishaug et al., J. Biomed. Mater. Res. 28:1445, 1994). Seeded compositions have also been studied for their utility in bladder control and vesicoureteral applications (see, for example, Griffith-Cima et al., published PCT application no. WO 94/25080.
Researchers in the field have identified several characteristics that are desirable for scaffold materials to be used in such seeded compositions. For example, Freed et al. (Bio/Technology 12:689, 1994) list the following six factors as desirable features:
(1) the scaffold surface should permit cell adhesion and growth; PA1 (2) neither the scaffold material nor its degradation products should provoke inflammation or toxicity when implanted in vivo; PA1 (3) the scaffold material should be reproducibly processable into three dimensional structures; PA1 (4) the scaffold material should have a porosity of at least 90% so that it provides high surface area for cell-scaffold interactions, sufficient space for extracellular matrix regeneration, and minimal diffusion constraints during in vitro culture; PA1 (5) the scaffold material should resorb once it has served its purpose of providing a template for the regenerating tissue; and PA1 (6) the scaffold degradation rate should be adjustable to match the rate of tissue regeneration by the cell type of interest.
Much effort has been spent in attempts to identify materials that can act as effective scaffolds for tissue repair. There remains a need for the development of suitable new materials for use as scaffolds in cell seeding applications.